Abstract : The report contains a description of an apparatus and a technique that can be used to determine the presence of alkane hydrocarbons from C3 to C6 which are dissolved in an aquatic environment. The apparatus is a gas-stripping device which continuously removes the hydrocarbon vapors from water and injects them into a gas chromatograph. The gas chromatograph separates and detects the components present in the stripped vapors. The instrument was to be suitable for use by the Coast Guard in surveillance operations, to detect the presence of hydrocarbons in the water, to be used in monitoring clean-up operations following an oil spill, and to measure the dissolved hydrocarbons remaining after apparent complete removal of oil from the water surface.